Solid freeform fabrication (SFF) or layer manufacturing (LM) is a fabrication technology that builds an object of any complex shape layer by layer or point by point without using a pre-shaped tool (die or mold). This process begins with creating a Computer Aided Design (CAD) file to represent the geometry of a desired object. SFF technology enables direct translation of the CAD image data into a three-dimensional object. SFF technology can be used in applications such as verifying CAD database, evaluating design feasibility, testing part functionality, assessing aesthetics, checking ergonomics of design, aiding in tool and fixture design, creating conceptual models and sales/marketing tools, generating patterns for investment casting, reducing or eliminating engineering changes in production, and providing small production runs.
One SFF technique involves adding or depositing a build composition to form predetermined areas of a layer essentially point-by-point; but a multiplicity of points may be deposited at the same time in some techniques (e.g., ink-jet technology). These predetermined areas together constitute a thin section of a three-dimensional object as defined by a CAD geometry. Successive layers are then deposited in a predetermined sequence with a layer being affixed to its adjacent layers forming an integral three dimensional, multi-layer object.
Typically, an SFF system includes a dispensing system such as an ink-jet dispensing system, a curing system, and a build platform. The build composition is stored within a compartment of the ink-jet dispensing system as a mixture of an initiator and a build material. The build composition is dispensed (i.e., jetted) onto the build platform from an ink-jet printhead of the ink-jet dispensing system.
Currently, the build compositions used in the SFF processes are limited to low viscosity materials (i.e., typically lower than 20 centipoise (cps) for good jetting) so that the build composition can be accurately dispensed. Viscosity is an important parameter for dispensing materials because materials having a high viscosity are difficult to dispense. One way to overcome problems associated with viscosity is to increase the dispensing temperature of the material. However, some of these build compositions degrade at the higher temperatures. In addition, heating the build compositions may initiate polymerization of the build composition prior to being dispensed. Therefore, build compositions with high viscosities that are unstable at higher jetting temperatures cannot be used.